The invention relates to vinylidene-containing polymers and methods of making such polymers. The invention also relates to the applications of the vinylidene-containing polymers, especially in formulating lubricant oils.
Synthetic hydrocarbons have been used as lubricants for automotive, aviation, and industrial applications. In the automotive industry, lubricant oils include engine oils, brake fluids, and lubricating greases. Engine oils for an automobile include 2-stroke oils, 4-stroke oils, and gear oils. In the aviation industry, lubricant oils include turbine oils, piston engine oils, hydraulic fluids, and lubricating greases. In industrial applications, lubricant oils are used as gas-turbine oils, gear oils, bearing and circulation oils, compressor oils, hydraulic oils, metal-working fluids, heat-transfer and insulation oils, and lubricating greases.
Polyisobutenes and poly-xcex1-olefins are two notable synthetic hydrocarbons which have been used as lubricant oils. Poly-xcex1-olefins have good flow properties at low temperatures, relatively high thermal and oxidative stability, low evaporation losses at high temperatures, high viscosity index, good friction behavior, good hydrolytical stability, and good erosion resistance. Poly-xcex1-olefins are not toxic and are miscible with mineral oils and esters. Consequently, poly-xcex1-olefins are suited for use in engine oils, compressor oils, hydraulic oils, gear oils, and greases. However, poly-xcex1-olefins have limited biodegradability and limited additive miscibility. Therefore, it may not be suitable for use as high-performance gear oils and fast biodegradable oils. Structurally, poly-xcex1-olefins often include tertiary hydrogen which is prone to oxidation. Therefore, it would be desirable to eliminate the presence of tertiary hydrogen so as to improve oxidation resistance to synthetic hydrocarbons.
Polyisobutenes are another type of synthetic hydrocarbon which have been used as lubricant oils. Polyisobutenes offer good lubrication properties and good corrosion resistance. Polyisobutenes are not toxic and are miscible with mineral oils. However, polyisobutenes have relatively low oxidation stability and relatively poor flow properties at low temperatures. They also have relatively high evaporation losses and low viscosity indices. Consequently, polyisobutenes are suitable for 2-stroke engine oils, compressor oils, metal-working lubricants, greases, and wire rope lubricants; but they are not suitable for most circulation-system lubricants. In addition, polyisobutenes are known to depolymerize at elevated temperatures, a phenomenon known as xe2x80x9cunzipping.xe2x80x9d Generally, depolymerization occurs above 250xc2x0 C. This unzipping phenomenon precludes use of polyisobutenes at elevated temperatures. Therefore, it would be desirable to avoid the unzipping of polyisobutenes, while retaining the benefits associated with polyisobutenes.
A copolymer of xcex1-olefin/isobutene may offer an alternative to polyisobutene and poly-xcex1-olefins. For example, an ethylene/isobutene copolymer would not include tertiary hydrogen. Thus, such copolymer may have improved oxidation resistance. Furthermore, the incorporation of ethylene units may prevent or alleviate the unzipping phenomenon associated with polyisobutenes. However, such copolymers have not been available because many vinylidene olefins, such as isobutene, do not copolymerize in the presence of a Ziegler-Natta catalyst. Therefore, there is an unfulfilled need to explore the possibility of making vinylidene-containing polymers for various applications.
Embodiments of the invention described herein meet the above need by providing various vinylidene-containing polymers, preferably obtained in the presence of a single-site catalyst. Methods of making and using the vinylidene-containing polymers also are provided herein. Such polymers have a wide range of applications. Properties and advantages associated with embodiments of the invention become apparent with the following description.